Rust temp fix until I can repair properly?

[JoshT]

That seems an odd spot for rust on the top side of the cab crossmember, have you determined what caused it?

Not yet, it was getting dark fast. I was more focused on cleaning out a decade of rat poop and probably two decades or dirt. I suspect it might be rain water leaking around the back window or the cargo light. I'll be trying to figure that out this weekend if weather allows.

I would also suggest going on the underside with a piece of scrap metal or flashing, coated or painted, put a bead of RTV around it and screw it to the bottom with some sheet metal screws or panel bond adhesive.

That's the plan if I can get to it. Not much point in treating one side if the other is left alone.

[Ranchero50]

I would also suggest going on the underside with a piece of scrap metal or flashing, coated or painted, put a bead of RTV around it and screw it to the bottom with some sheet metal screws or panel bond adhesive. That would keep road water from getting inside.

It's just more crap to deal with during the next repair. Steel doesn't rust much of left alone. it's when it has a nice coating of 'something' for the moisture and corrosion to dig into that you have problems. The 1/4 panels in my Ranchero went 20 years without rusting away to pieces once I ground the old bondo out and painted them. I was surprised how well they lasted, especially with the duty it did.

[sargentrs]

You've got a point there, Jamie When I replaced my floor pans I spent HOURS removing "something" a PO had undercoated over the rust. Nasty!

[JoshT]

Oh no, I'm not suggesting to put undercoat or Bondo, or even JB weld on there.

I'm talking coating I'm talking about is the rust converter stuff that "transforms" rust into a black oxide primer. Then going over that with rattle can paint. Final step of covering the hole will be to apply some foil tape over the hole to keep out the elements.

[Ranchero50]

Never had any luck with the converter stuff. You need to grind the flaky rust away or there's an unconverted layer of muck for the rust to craw under the converted layer and have it's way with your floor again. I did old nasty non environmentally friendly black roofing tap under my cab and it's held up pretty well. Anywhere I painted over a bit of rust it's come through but the tar has kept the moisture from getting to it. Next year I plan on going over my cab again and fixing some stuff I thought I didn't need to dig into like the roof cap where some specks turned into flakes once painted and the door that had some little zits all over that have came back through the Rustoleum paint (that's supposed to stick to rust...)